Mag-oxy cements, as for example, magnesium oxychlorides, magnesium oxysulphates, and magnesium oxycarbonates have long been known to be desirable binders which have high strength and do not burn; but in the past have had the deficiency of poor weathering characteristics. A number of attempts have been made, and patents have issued, on ways of improving the weatherability of mag-oxy cements. To my knowledge, none have truly produced an insoluble material capable of long exposure to the weather.
In the attempts which have been made to improve the weatherability of mag-oxy cements, some researchers have added silicic acid as in the Gallinowsky U.S. Pat. No. 723,263. In the Groyen U.S. Pat. No. 771,062, water glass was added. Sohl et al U.S. Pat. No. 2,351,641 appears to teach that various phosphates react with lime to prevent leaching of lime from cements, as occurs in concrete and the like. In the Moore and Watts U.S. Pat. No. 2,479,504, the addition of an acid phosphate is suggested; and the patent further indicates that a reaction between the metal oxides and the acid phosphates ensues at normal temperatures to form an insoluble phosphate. I, however, have found that acid phosphates produce products that are more soluble than when orthophosphates are used. In Eastin U.S. Pat. No. 2,543,959, one percent sodium pyrophosphate is suggested to provide a protective film around the magnesia particles to prevent them from contracting during cure. Prior U.S. Pat. No. 3,320,077 suggests that sodium hexametaphosphate is a celating agent for magnesium oxide to in turn control its hydration and reaction in forming the basic magnesium oxide cement. In all of the prior art with which I am familiar, a reaction of magnesium oxide with magnesium chloride, magnesium sulphate, or a carbonate is carried out in an aqueous medium at atmospheric temperatures. In checking the reactions of the materials suggested by the prior art, however, I have found none that give a truly insoluble cement.
An object of the present invention, therefore, is the provision of a new and improved mag-oxy cement, and method of making same, which is nonleachable, and which has sufficiently good weathering properties that it can be used as a binder for glass fibers to produce a material comparable in strength, durability, and weatherability to that of the polyester resins.
Another object of the invention is the provision of a new and improved method of making mag-oxy molding compounds which will give products of increased durability.
Further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments.